Identification of novel compound heterozygous variants in the SLC30A7 (ZNT7) gene in two French brothers with stunted growth, testicular hypoplasia and bone marrow failure.

ABSTRACT

Zinc is an essential trace mineral. Dietary zinc deficiency results in stunted growth, skin lesions, hypogonadism and frequent infections in humans. Mice genetically lacking Slc30a7 suffer from mild zinc deficiency and are prone to development of prostate cancer and insulin resistance. Disease-causing variants or mutations in the human SLC30A7 (ZNT7) gene have not been previously reported. Here, we describe two-boy siblings from a French family with stunted growth, testicular hypoplasia and bone marrow failure. Exome sequencing revealed compound heterozygous variants in ZNT7 consisting of NM_133496.5c.21dup; p.Asp8ArgfsTer3 and c.842 + 15 T > C inherited from their unaffected mother and father, respectively. The c.21dup variant led to a premature stop codon generated in exon 1 of the ZNT7 coding sequence. RNA-seq analysis demonstrated that the c.842 + 15 T > C variant resulted in a leaky mRNA splicing event generating a premature stop codon right after the splicing donor site of exon 8. Moreover, the expression of ZNT7 protein was remarkably reduced by 80-96% in the affected brothers compared to the control cells. These findings strongly suggest that biallelic variants in SLC30A7 should be considered as a cause of growth retardation, testicular hypoplasia and syndromic bone marrow failure.